The present invention relates to a portable, self-contained, X-ray apparatus that digitally processes, displays, stores, and/or transmits electronic radioscopic images of sealed packages, containers, or other objects, or of patients and animals, on location for security, customs, medical, and other non-destructive and non-invasive purposes. More particularly, the present invention relates to an enhanced X-ray converter screen for use in X-ray radioscopic imaging systems which increases the detected brightness and reduces the effects of veiling glare and multiple reflections through the use of thin film lenslets or other light directing films or structures which simultaneously modify the emission angle of light from the screen and change its reflective characteristics to external light through the use of thin film lenslets or other light directing films or structures which simultaneously modify the emission angle of light from the screen and change its reflective characteristics to external light.
There are many instances in the medical, security or customs field when it is necessary to examine or inspect, in a non-invasive way, a patient, animal, or other living organism; or to examine and inspect, in a non-destructive way, the contents of a closed package, box, suitcase, or other container. Some of the general concerns and problems associated with such examinations or inspections are set forth in U.S. Pat. No. 5,608,774, incorporated herein by reference.
Where the imaging system uses an objective lens coupled through a collection cone to a phosphor X-ray conversion screen, as is common in many radioscopic imaging systems, there is a continuing need to improve the brightness and contrast of the displayed image. This is because such systems are premised on the assumption that all of the emitted light from the phosphor screen is collected into the collection cone of the objective lens, thereby providing a clear, sharp image of the emitted light. In practice, however, some of the emitted light is not collected into the collection cone and is scattered by objects within the imager enclosure back onto a different portion of the phosphor screen, from which location it is then diffusely reflected, with a fraction of the light being sent back into the collection cone. Since this light appears to originate from a differing point on the phosphor screen, it effectively reduces the true contrast of the image.
Virtually all optical designs are plagued by the problem of light outside of the capture cone of the lens hitting other features within the optical system and being scattered back into the image. Generally, prior art designs attempt to solve this problem by making the walls of the system physically distant from the beam, using a series of anti-scatter baffles just outside of the optical path, and coating all surfaces with a very non reflective material. The literature contains designs for such systems as well as the formulations of paints and surface treatments for accomplishing these goals.
Unfortunately, the above approaches are very difficult to use in a mirror folded system, such as is used for many X-ray imaging systems, including the present invention. Further, if one wants to restrict the depth of the optical system (which is the case with the present invention) by using a mirror angle of 45 degrees or less, the problems of containing the light emitted at angles that would normally not fall into the collection cone and keeping this light from reflecting back onto the diffuse phosphor surface (where it may then bounce back into the collected beam) becomes virtually impossible.
It is thus evident that improvements are needed within X-ray radioscopic imaging systems, as well as any imaging system that uses light emitted from a diffuse phosphor screen into the collection cone of an objective lens, that both: (1) increase the fraction of light from the phosphor converter screen that is collected into the collection cone of the objective lens, and (2) which reduce the effects of light emitted from the diffuse phosphor screen not captured by the lens.
The present invention addresses the above and other needs.